Problem with starting my 420 SE (W126)

Cold or warm, I often experience some difficulties starting the engine: at the first crank it's revs up and immediately drops dead. When I try again it won't start anymore. After insisting serveral
minutes, it starts running again, quite normally.
Battery is good and enough fuel is in the reservoir.
What could this be: a mechanical or electronical problem...??
Do you have any ideas for me, please.
Thanks in advance
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Some M-B cars have an electric relay that causes strange, inexplicable behavior when it malfunctions; it's called the "over voltage protection relay".
You can locate it by looking for a relay box with a fuse mounted on its top.
It's a likely suspect if it is original to the car.
I hope this helps solve the problem.
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Find your fuel pump relay in the fuse box... it is the biggest black relay with the word 'kickdown' on it... on the side, it will stamp the date of manufacture... if it is the same year as your car or at least 10 years old... buy a new one or swap with a working one to test.
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